1. Field of the Invention
This invention relates to tobacco expansion agents and to tobacco expansion processes.
2. Brief Description of the Prior Art
It is a well-established practice in the tobacco industry to subject tobacco to a process which results in an increase in the filling power of the tobacco. Such a process is often referred to as a tobacco expansion process. In prior proposed tobacco expansion processes, tobacco lamina or tobacco stem is impregnated with an expansion agent. Thereafter the tobacco may be subjected to a heating step, usually comprising contact between the tobacco and a heating medium such, for example, as hot air and/or steam. The heating step effects removal of the expansion agent from the tobacco. In some of these expansion processes, it is during such a heating step that the expansion of the tobacco takes place.
As an alternative to a heating step, the tobacco, initially at an elevated pressure and temperature, may be subjected to a sudden reduction in pressure. A further alternative is freeze-drying.
Among the expansion agents used in prior proposed expansion processes are water, steam, air, nitrogen, carbon dioxide, sulphur dioxide, ammonia, hydrocarbons and halogenated hydrocarbons.
According to a tobacco expansion process described in United Kingdom Patent Specification No. 955,679, tobacco is subjected to a solvent in liquid form selected from the group comprising aliphatic hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, alcohols, ketones, ethers, esters, chlorinated solvents and combinations of said group of solvents which are miscible. The liquid solvent is removed by, for example, blowing air through the tobacco.
In U.S. Pat. No. 3,693,631 there is described a tobacco expansion process in which a volatile organic compound or compounds is/are used to impregnate the tobacco. According to the teaching of this specification, preferred organic compounds are non-oxygenated compounds which are relatively non-polar and relatively or substantially immiscible in water.
In U.S. Pat. No. 3,425,425 there is described a process for expanding tobacco stems in which the stems are treated with a solution comprising one or more sugars and one or more of a sodium or potassium salt of an inorganic or organic acid, a mono or di-basic acid or sodium or potassium hydroxide. After treatment with the solution, the stems are dried and then heated to a temperature of, for example, 300.degree. C.
A tobacco expansion process in which tobacco is treated with ammonia and carbon dioxide is described in U.S. Pat. No. 3,771,533. The ammonia and carbon dioxide treated tobacco is then heated and/or subjected to reduced pressure.
In Publication Document No. 107,932 of European Patent Application No. 83305989.2 there is a description of a tobacco expansion process in which tobacco is treated with an expansion agent in the vapour phase under elevated temperature and pressure conditions. Subsequently the pressure is released. The preferred expansion agents are the light hydrocarbons, ethane, propane, propylene, n-butane, isobutane, dichlorodifluoromethane and monochlorodifluoromethane. It is stated that mixtures of expansion agents may be used satisfactorily.
Although there has been mention in the patents literature of the use in tobacco expansion processes of expansion agents comprising two or more components, there has, to the best of our knowledge, been no teaching of the provision of a tobacco expansion agent comprising first and second components which is capable of producing a synergistic effect in terms of tobacco filling power increase when employed in a tobacco expansion process. For a two-component expansion agent to exhibit synergism, the filling power increase effected by the agent would have to be greater than the increase expected on a linearly proportional basis from the increases for each of the components.
It is an object of the present invention to provide tobacco expansion agents which exhibit synergism.
It is a further object of the present invention to provide tobacco expansion agents comprising first and second components, in the use of which agents in tobacco expansion processes, increases in tobacco filling power are obtainable which are greater than would be obtained using either of the first and second components alone.